Under the influence of earth curvature, the localization error of traditional positioning model based on rectangular plane coordinate system will increase significantly with the detection range increasing, and it seriously affects the positioning and tracking accuracy of long-range targets. This paper proposes a positioning method with single moving platform based on spherical models. It transforms the plane rectangular function equation into the spherical trigonometric function equation to reduce the influence of the earth curvature error. It utilizes the Unscented Kalman Filter(UKF) algorithm to solve the complicated nonlinear observation equation iteratively and realizes high-precision position estimation of long-range targets. Simulation results demonstrate that the proposed method based on spherical models has a higher position accuracy which is increased by 0.3%R~0.6%R.